linux-kernel - Re: [PATCH v13 02/13] irqchip/sifive-plic: Improve locking safety by using irqsave/irqrestore

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Date: Tue, 20 Feb 2024 11:11:19 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Anup Patel <apatel@...tanamicro.com>, Palmer Dabbelt
 <palmer@...belt.com>, Paul Walmsley <paul.walmsley@...ive.com>, Rob
 Herring <robh+dt@...nel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@...aro.org>, Frank Rowand
 <frowand.list@...il.com>, Conor Dooley <conor+dt@...nel.org>
Cc: Marc Zyngier <maz@...nel.org>, Björn Töpel
 <bjorn@...nel.org>, Atish
 Patra <atishp@...shpatra.org>, Andrew Jones <ajones@...tanamicro.com>,
 Sunil V L <sunilvl@...tanamicro.com>, Saravana Kannan
 <saravanak@...gle.com>, Anup Patel <anup@...infault.org>,
 linux-riscv@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, Anup Patel
 <apatel@...tanamicro.com>
Subject: Re: [PATCH v13 02/13] irqchip/sifive-plic: Improve locking safety
 by using irqsave/irqrestore

On Tue, Feb 20 2024 at 11:37, Anup Patel wrote:
> Now that PLIC driver is probed as a regular platform driver, the lock
> dependency validator complains about the safety of handler->enable_lock
> usage:
>
> [    0.956775]  Possible interrupt unsafe locking scenario:
>
> [    0.956998]        CPU0                    CPU1
> [    0.957247]        ----                    ----
> [    0.957439]   lock(&handler->enable_lock);
> [    0.957607]                                local_irq_disable();
> [    0.957793]                                lock(&irq_desc_lock_class);
> [    0.958021]                                lock(&handler->enable_lock);
> [    0.958246]   <Interrupt>
> [    0.958342]     lock(&irq_desc_lock_class);
> [    0.958501]
>                 *** DEADLOCK ***
>
> To address above, let's use raw_spin_lock_irqsave/unlock_irqrestore()
> instead of raw_spin_lock/unlock().

s/let's//